Domestic Equids Can Still 'Chill' Like Their Ancestors

Recent study results indicate that horses can still slow their body processes to conserve energy when food is short and temperatures are cold, an important survival characteristics for their wild ancestors.

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While today's domestic horses rely on humans for many of their survival needs, a recent study by researchers in Germany demonstrated that domestication has not removed all their "wild" abilities. The results of the study, led by Lea Brinkmann, MSc, and colleagues at the University of Göttingen in Germany, indicate horses can still slow their body processes to conserve energywhen food is short and temperatures are cold, important survival characteristics for their wild ancestors.

Although research has revealed signs of hypometabolism, or slowing of body processes, in the Przewalski horse, the closest living wild relative of the domesticated horse, previous research suggested that today's livestock had lost that ability because selection pressure was not needed to maintain it.

For the current year-long study, Brinkmann and her team evaluated 10 domestic Shetland ponies accustomed to outdoor housing. The ponies, aged 4 to 16 years, resided in semi-natural outdoor conditions: pasture in summer and paddocks with open stables in winter.

In summer the ponies had access to water and grass and were provided with hay, straw, and a mineral supplement. In winter the researchers split the ponies into one control group and one feed-restricted group to simulate natural seasonal food shortages; the feed-restricted group received first 80%, and then 70%, of recommended energy and protein requirements. Researchers recorded the ponies' ambient temperature, subcutaneous temperature, locomotor activity, lying time, resting heart rate, body mass, and body condition score.

The team found that the feed-restricted ponies exhibited reduced heart rate and subcutaneous temperatures in the winter, which are both signs of hypometabolism. The researchers concluded that domesticated horses, through seasonal fluctuations in their metabolic rate, can still adapt to seasonal environmental conditions.

"Domesticated ponies have retained the ability to adapt to harsh winter conditions like their wild ancestors, so year-round outdoor housing can be an adequate housing system for robust ponies," said Brinkmann. "However, despite the adaption ability, it is essential to provide adequate food and to carefully inspect body conditions when domestic ponies are housed outdoors year-round to counteract possible welfare problems."

The study, "Adaptation strategies to seasonal changes in environmental conditions of a domesticated horse breed, the Shetland pony (Equus ferus caballus)," was published in the April 2012 issue of The Journal of Experimental Biology. The abstract is available online.